Ventilators are used to dissipate heat from a subrack, said ventilators generating a forced air flow which is directed past the component groups to be ventilated. RPM-regulated electrical drives which are controlled by a control unit are generally used.
The reliability of a system with electronic and/or electrical component groups depends decisively on the operability of the ventilation system. If the ventilation system fails, local overheating of components takes place, which consequently results in functional impairments or in a total system failure.
In safety-critical systems, it is conventional for ventilation systems to be configured redundantly. Several ventilators are operated in parallel, each being controlled by redundantly configured control electronics. Speed-regulated electromotors are generally used. Speed regulation is carried out by means of a switching element arranged in the power circuit of the connecting wires, said switching element being clocked for instance using pulse width modulation. Even if for reasons of cost the rotational speed is determined only at a master drive and fed back to the controller, the redundantly configured control electronics require a cost outlay which is too large for many applications.
Patent specification U.S. Pat. No. 6,021,042 discloses a ventilation device comprising two ventilators connected in parallel in order to dissipate the heat from electronic component groups of a computer. Each ventilator produces an air flow which is directed onto two processor component groups to be ventilated, via a mixing chamber. Swing-type check valves are arranged in the mixing chamber such that in the event of a fault, each air flow produced can be directed respectively onto one of the processor component groups to be cooled. There are applications for which the mechanical outlay for the mixing chamber and the air baffle devices connected thereto is too big and/or the required space is not available.
In many cases the mechanical components of the air generating device are also already integrated into the subrack and specified by the manufacturer. To increase fault tolerance it is possible to configure only the control electronics redundantly on the user side.